1. Field of Invention
This invention relates to a transportation system, generically known as Personal Rapid Transit, which employs conventional electric or hybrid automobiles under which are mounted electro-mechanical guideway adaptors, which permits them to operate autonomously on an elevated guideway which is part of the PRT system. An electronic guidance sensor system, and other functional components built into the adaptors, permits the vehicles to track unique rf signals emitted from a guidance wire centrally embedded in the guideway, and to enter and exit the guideway from off-line stations and to select various platforms and storage areas within these stations.
2. Description of Prior Art
A variety of ground transportation systems have been developed and put into practice since the advent of the industrial revolution. Private automotive transit has become the method of choice for most commuters throughout the world wherever circumstances permit. The result has been excessive congestion on the highways, traffic delays, and pollution. Despite these facts, mass transit, in the form of rail or bus, has run a very poor second because of high costs and relative inconvenience. This under-utilization has spiraled into even poorer performance for our mass transit systems.
Within recent years, specifically with the advent of efficient electric and hybrid vehicles, inexpensive and reliable computers, and digital communications, a form of mass transit known as Personal Rapid Transit (PRT), which has been in the open literature for many years, has become technically feasible. It eliminates many of the major deficiencies and inconveniences of current mass transit systems. Its salient, and most desirable characteristics from a commuter standpoint include an elevated guideway not vulnerable to normal traffic congestion, with access to this guideway by small, self-contained automated vehicles obtainable at convenient off-line stations. These vehicles can be available on a demand basis, 24 hours per day (24/7), overcoming one of the major faults of current commuter systems which adhere to rigid schedules and frequent stops. Once a vehicle is acquired at an off-line station, and the destination entered into the vehicle computer by either keypad or voice, the vehicle will proceed non-stop to its final destination. Off-line stations can be configured to be accessible by private vehicles adapted to be compatible with the guideway system requirements. The guideways are constructed along the shoulders or rights of way of existing roads or rail corridors, thereby requiring no additional real estate. The footprint is very small.
Initial prior art investigated include: U.S. Pat. No. 5,063,857 to Kissel, Jr. (1991) describes in the narrative of his "Comprehensive Unit Transportation System" most of the features and virtues of PRT. It should be noted that the operational concept of PRT, as described, has been well documented in the open literature for several decades prior to this patent. Specifically, however, the proposed implementation requires a highly specialized vehicle which does not take advantage of the innumerable engineering hours that have gone into the modern automobile. This is very undesirable from an ultimate system production cost standpoint. Also, the vehicle switching system in his patent is dependent upon the motion of a hinged section of the guideway. This is undesirable from a safety and reliability standpoint considering that on a busy PRT commuting system this action may be required several thousand times per day at very rapid rates. It is mandatory to keep the guideway totally passive. U.S. Pat. No. 4,061,089 to Sawyer (1977) with the specific title "Personal Rapid Transit System" describes a unique operational implementation combining frictionless vehicles floating by compressed air over a linear synchronous motor on a specialized conforming guideway. Both the guideway and the vehicle are non-standard and would be very expensive as a production item. As a result, this system has never been implemented. U.S. Pat. No. 5,794,535 to Pardes (1998) "Switching Mechanism For Transit Modules" overcomes the need for any mechanical motion of the guideway at any time, and permits reliable, computer controlled switching at exit and merge points. However, configuration and installation of the electro-magnetic switching mechanism within the vehicle has proven to be sufficiently complex to necessitate major modifications to any standard automobile. Also, the necessity of a mechanical base guide for vehicle guidance is an undesirable feature which increases noise, both audible and electrical, and may decrease overall system reliability. A modification of some of the switching features of this design are incorporated in this invention disclosure. Considering the guidance aspect of the transit vehicle, U.S. Pat. No. 5,318,143 to Parker (1994) "Method And Apparatus For Lane Sensing For Automatic Vehicle Steering" does employ a standard automobile however an active electro-optical system is designed to sense a center stripe on a highway. This is unacceptable and deficient for a system where there are multiple branches and where weather conditions may deteriorate, or obliterate, the strip contrast. U.S. Pat. No. 4,083,422 to Blakeslee (1978) "Bolt-On Guidance System For Lift Truck" describes an automatic guidance device which follows a single radiating wire path embedded in the floor of a warehouse or similar facility. The general technique may be valid for PRT use but is deficient since there is no means of providing branch paths which can be computer selected. The vehicle, of course, is not a standard automobile.
In addition prior art cited, all of the approaches imply the need for a specialized vehicle and mechanical switching and guidance systems. All of the patents reviewed in the prior art such as U.S. Pat. Nos. 4,671,185 (1987 ) and 4,522,128 (1985) to Anderson, U.S. Pat. No. 5,138,952 (1992) to Low, U.S. Pat. No. 5,277,124 (1994) to DiFonso, U.S. Pat. No. 4,132,175 (1979) to Millerl/Westinghouse, and U.S. Pat. No. 4,991,516 (1991) to Rixen fail to meet the requirements of a viable vehicle and guideway combination for a reliable PRT system with the safety features mandatory for a public mass transit system, or for the employment of a standard automobile which is necessary for a cost-effective commercial product. Minakami et al, U.S. Pat. No. 6,129,025 (Oct. 10, 2000), employs a carrier pallet which rides on a guideway on which any type of vehicle or container can be driven and from there on automatically forwarded to its final destination. It has many of the attributes of a PRT system but has a major deficiency in that commuters must access the pallet with their own vehicle which negates the philosophy of mass transit which is intended to reduce the number of vehicles on the road, and it also should be accessible to the general public who may not have cars or the ability to drive. Also, the pallet and guideway combination are quite complex and may prove to be overly expensive in construction and maintenance. Similarly Barratt, U.S. Pat. No. 5,199,358 (1993) "Vehicle Guideway and System for Mass Transit" utilizes a piggyback operation on which vehicles are attached to electrically operated sled modules. Here again the commuter must have his own vehicle and the guideway becomes relatively complex. System communication, as required in a PRT system, is inherent in Gagnon et al, U.S. Pat. No. 3,979,091 (1976) however this design does not provide accurate lateral vehicle position within the narrow confines of a guideway. The patent was not intended for that purpose. A form of system communication via a transmission line along the guideway, or wayside, as described may be employed. It is not claimed in this patent.